fix orElseThrow does not accept a function

Author: laspt

package-lock.json

@@ -1,6 +1,6 @@
 {
     "name": "@lassepitkanen/optionalts",
-    "version": "1.0.3",
+    "version": "1.0.4",
     "description": "TypeScript library that provides an Optional<T> type similar to Java's Optional class.",
     "author": "Lasse Pitkänen",
     "license": "MIT",

package.json

@@ -132,13 +132,13 @@ describe('Optional', () => {
     describe('orElseThrow', () => {
         it('should return the value of a Some', () => {
             const optional = Optional.of('hello');
-            const value = optional.orElseThrow(new Error('should not throw'));
+            const value = optional.orElseThrow(() => new Error('should not throw'));
             expect(value).toBe('hello');
         });
 
         it('should throw the given error for a None', () => {
             const optional = Optional.empty();
-            expect(() => optional.orElseThrow(new Error('should throw'))).toThrowError('should throw');
+            expect(() => optional.orElseThrow(() => new Error('should throw'))).toThrowError('should throw');
         });
     });
 

src/optional.spec.ts

@@ -86,7 +86,7 @@ export abstract class Optional<T> {
      * @returns The content of this Optional if it is not empty.
      * @throws The specified error if this Optional is empty.
      */
-    abstract orElseThrow<K extends Error>(error: K): never | NonNullable<T>;
+    abstract orElseThrow<K extends () => Error>(func: K): never | NonNullable<T>;
 
     /**
      compares this optional with another to determine equality.
@@ -172,7 +172,7 @@ export class None<T> extends Optional<T> {
         return func();
     }
 
-    orElseThrow<K extends Error>(error: K): never {
-        throw error;
+    orElseThrow<K extends () => Error>(func: K): never {
+        throw func();
     }
 }